The invention relates in general to piston vibrators employed to cause ordinarily non-flowing granular materials to move and more particularly to a pneumatic piston vibrator of the impact type combining great force with low decibel noise level during operation.
Not all materials flow unaided through troughs, chutes, bins or hoppers with the speed desired. It has long been recognized that pneumatic piston vibrators fixed to one of the above enumerated retainers along which the material is meant to flow will accelerate the materials' movement by relaying the force of impact of a reciprocating piston housed inside a vibrator piston chamber, through the vibrator housing mounted on the retainer surface to the material itself.
Pneumatic piston vibrators are of various generic types classed by the mode of cushioning of the piston in the vibrator piston chamber. Impact pneumatic piston vibrators allow the piston to strike the chamber extremity at one end of the stroke while preventing impact at the other end of the stroke by means of a cushion of pressurized air. The silent pneumatic piston vibrator introduces a cushion of pressurized air at each end of the piston stroke, preventing piston impact at either end of the piston chamber.
Some of the problems and requisites that should be considered in designing a pneumatic piston vibrator are as follows:
The vibrator housing transmits force to the material sought to be moved. The piston generates that force. The greater the force, the greater the material influencing efficiency of the vibrator. The impact type piston strikes the piston chamber extremity directly and thereby generates force in the area of 107 lbs. The silent type piston never strikes either chamber extremity. The pressurized air cushion reduces the force generated to the area of 100-1000 lbs.
The Occupational Safety and Health Administration has promulgated regulations on the noise level in decibels acceptable in industrial occupational settings. That decibel limit is currently approximately 90 dba. An impact vibrator will produce noise in the area of 105-110 dba. A silent type vibrator will produce approximately 40-65 dba.
Both types of pneumatic piston vibrators offer problems. By allowing the piston to strike a chamber extremity, the impact type generates more impact force and a more efficient material influencing vibrator but the decibel level is high and unacceptable. The silent type pneumatic piston vibrator has significantly lower decibel level but the cushioning effect of the pressurized air produces a correspondingly low force of impact to be transmitted to the material.